Habituation.doc

Chapter 5: Learning and Behaviour
Habituation:
● we react automatically to events:
● orienting response – organism directs appropriate sensory organ toward
source of novel stimulus
● habituation – simplest form of learning: learning not to respond to an
unimportant event that occurs repeatedly
● George Humphrey – experiment with snails, got used to tapping so wouldnt
retreat into shell
● from evolutionary perspective – waste of time and energy
● Wicks and Rankin – used worm Nemoda and subjected them to taps or heat
 found that this withdrawing effect occurs through neurons that respond to
mechanical stimulus, regardless of stimulus
 could produce habituation to tap-elicited stimulus but not to heat – shows
they learned something about tap and could distinguish it from reaction to
source of heat
 only had 302 neurons in NS
● short term habituation – simplest form
● long term habituation – animals with more complex nervous system
● pattern of experience plays a role in distinguishing long-term and short-term:
 when sitmuli are massed into quick repetitions, habituation is rapid but ST
 when sitmuli are presented in small groups that are spaced over time,
habituation is slower but LT
 evidence that 2 different neural mechanisms are responsible for this
Classical Conditioning:
● invovled learning about conditions that predict that a significant event will
occur
● Pavlov – noticed dogs salivated when they saw research assistant come into
room so he set up experiment with bell and food and dogs learned to salivate
when they heard bell ring
● Classical Conditioning – process by which a response normally elicitied by
one stimulus (UCS) comes to be controlled by another stimulus (CS) as well
● sequence and timing is important
● unconditional stimulus – stimulus that naturally elicits a reflexive response
● unconditional response - behaviour itself that is naturally elicited by UCS
● conditional stimulus – stimulus that, because of repeated association with
UCS, eventually elicits conditional response
● conditional response – response elicited by CR
Biological Significance of Classical Conditioning:
● two funcitons:
 ability to learn to recognize stimuli that predicts occurence of an important
event allows learner to make appropriate response faster and more
effectively
■ siamese fighting fish more likely to win fight if they were given stimulus
(CS) that intruding male (UCS) would enter territory
■ blue gouramis more likely to mate sooner and produce more offspring when they received stimulus (CS) signalling approaching female (UCS)
■ learning that occurs with biologically significant UCS is more resistant to
subsequent modifications
 stimuli that were previously unimportant acquire some properties of
important stimuli with which they have been associated and thus become
able to modify behaviour
■ neutral stimulus becomes desirable when it is associated with desirable
stimulus or becomes undesirable when it is associated with undesirable
stimulus
■ specific properties of UCS become associated with CS - UCS takes on
symbolic value
■ Ward-Robinson – demonstrated this with pigeons where they pecked at
light when sound went on (paired sound CS with food UCS)
● adaptive significance is so general that even nematode exhibits it
● Wen – placed worms in solution of Na+ or Cl- with bacteria; when placed with
patches on ions and no bacteria, worm migrated to ions thinking there was
food
Basic Principles of Classical Conditioning:
● discovered 7 interesting phenomena: acquisition, extinction, spontaneous
recovery, stimulus generalization, and discrimination
Acquisition:
● acquisition – time during wich CR appears and increases in frequency
● strength of CR is influenced by: intesity of UCS and timing of CS and UCS
 more intense UCS produces rapid learning
 more intense UCS stronger the CR is
 classical conditioning occurs fastest when CS occurs shorlty before UCS and
both end at same time
 0.5 seconds is optimal delay between onset of CS and UCS
 little conditioning if CS follows UCS, or if too long or short delay will be
slower and weaker
Extinction and Spontaneous Recovery:
● extinction – elimination of a response that occurs when CS is repeatedly
presented without being followed by UCS
 participant learns that CS is no longer followed by UCS – if neither are
presented then extinction doesn't occur
 doesn't necessarily disappear permanently
● spontaneous recovery – after an interval of time, reappearance of response
that had previously extinguished
Stimulus Generalization and Discrimination:
● generalization – CR elicited by stimuli that resembles CS used in training
 once response has been conditioned to CS similar stimuli will also elicit that
response
 more stimuli resembles CS more likely it will elicit CR
● discrimination – appearance of CR when one stimulus is presented (CR+) but
not another one (CR-) accomplished by using 2 CS during training – one is
followed by the UCS and another isn't
 involes learning difference between 2 or more stimuli Conditioned Emotional Responses:
● many stimuli are able to arouse emotional response (disgust, contempt, fear,
anger, sadness, tenderness, longing, or sexual desire)
● many had no special signifance but were paired with stimuli that elicited strong
emotional reaction so they acquired emotional or evaluative signifance
● Todrank, Byrnes, Wrzesniewski, and Rozin – people associated pleasant
or unpleasant odour with attractive or unactriveness of person in photograph
● phobias – unreasonable fear of specific onjects or situations learned through
classical learning
 at some time early in life person was exposed to now-fearsome object in
conjunction with stimulus that elicited pain or fear
 classical conditioning can occur without direct experience with CS or UCS –
can be learned through observation (vicariously)
 imaginary episodes that we picture as we hear or read story (UCS) can
provide imaginary stimuli (CS) that lead to real conditional emotional
responses (CR)
 therapists use knowledge of principles of learning to eliminate them
 suggestions that biologically relevant stimuli are especially prone to
classically conditioned emotional responses
What is learned in Classical Conditioning:
● research shows that for classical conditioning to occur, CS must be reliable
predictor of UCS
● neutral stimulus becomes a CS only when following conditions are satisfied:
 CS regularly occurs prior to presentation of UCS
 CS does not regularly occur when UCS is absent
● principle has been clearly established by conditioning phenomenon known as
blocking
● blocking – prevention of or attenuation in learning that occurs to a neutral CS
when it is conditioned in presence of a previously conditioned stimulus
 CSA is paired with UCS, then new CSB is presented together with CSA and
compound of 2 stimuli is followed by UCS; compared to condition where CSA
has not been previously trained, CSB acquires little, if any, CR
 UCS is also predicted by CSA so CSB brings no new information about UCS –
would only provide new information if the UCS changed at same time CSB
was introduced
● classical conditionig provides two types of information: what and when of
future events
 what:
■ allows animals to learn that particular event is about to occur
■ behaviour is determined by memory of event
■ Hilliard and Domjan – examined conditioning of sexual behaviours in
male Japanese quail
● showed that male birds block of grey foam (CS) and then allowed
birds to interact with female bird (UCS) for 5 minutes; after several
such pairings males showed large increase in time they interacted
with CS object ● behaviour to CS was determined by males memory of UCS
● males were then given access to 8 birds for 40 minutes (satiated
condition) and others were given no access (deprived condition)
● when birds were later shown CS, satiated males gave less sexual
responses
● implies that what was learned involved memory of UCS – memory that
could be altered by subsequent experience such as satiation
 when:
■ if CS follows UCS, animal could learn that CS predict absence of UCS for
long period of time
■ if backward conditioning occurs, animals show inhibitory conditional
response as contrasted with excitatory conditional response
● inhibitory conditional response – reponse tendency conditioned to
signal that predicts absence of UCS; generally not observed directly
but assessed through other tests
● excitatory conditional response – response tendency conditioned
to signal that UCS is about to occur; type of CR exemplified Pavlov's
salivation response
■ learn something about timing of events during conditioning trial
■ Cole and Miller – trained rats in conditioned procedure in which
backward CSB followed UCS
● after substantial training, UCS was eliminated and a forward CSF was
presented just before CSB
● speculated that form of temporal integration would occur
● even though CSF had never been presented prior to UCS, rats
behaved as though it signalled upcoming UCS
● it associated the UCS and the CSB with the CSF
Operant Conditioning:
● operant conditioning – form of learning in which behaviour is affected by its
consequences; favourable consequences strengthen behaviour and
unfavourable consequences weaken behaviour
 relations between environmental stimuli and our own behaviour (operant –
organism learn through responding, through operating on environment)
The Law of Effect:
● Edward Thorndike set up lab with cat in William James's basement
 taught cat to open latch of box to get food
 called “learning by trial and accidental success”
 cat learned to make correct responses only because they were followed by
favourable outcome
● law of effect – consequences of behaviour determine whether it is likely to be
repeated
 like natural selection in sense that it determines which behaviours will
survive
● Skinner – selection of consequences: ability to adjust behaviour to fit changes
in environment is highly adaptive
● behaviour analysis – understanding behaviour-environmental interactions Skinner and Operant Behaviour:
● Skinner – advocated study of law of effect and applications of behaviour
analysis and its methods to solving human problems
● devised objective methods for studying behaviour, invented apparatus and
methods for observing it, and created own philosophy for interpreting it
● wrote several books, and novel Walden Two that showed how we could use it
to better society
● operant chamber – apparatus devised in which animal's behaviour can be
easily observed, manipulated, and automatically recorded
 provides unconstrained opportunity for simple response to be performed by
animal
● behaviour analysts manipulate environmental events to determine their effect
on response rate (number of responses emitted during given amount of time)
● events that increase response rate are said to strengthen responding and
events that decrease response rate are said to weaken responding
● cumulative recorder – mechanical device connected to opperant chamber
for purpose of recording operant responses as they occur in time (measures
response rate)
● better than Thorndike:
 participants can emit responses more freely over greater period of time
 participants can be studied for longer periods of time without interferce
produced by researcher handling or otherwise interacting with them
between trials
Three-Term Contingency:
● discriminative stimulus – stimulus that sets occasion for responding
because, in past, behaviour produced certain consequences in presence of that
stimulus
 say word “speak” and give dog food when he barks
● three-term contingency – relation among discriminative stimuli, behaviour,
and consequences of that behaviour; a motivated organism emits specific
response in presence of discriminative stimulus because, in past, that response
has been reinforced only when disrcriminative stimulus is present
 discriminative stimulus sets occasion for response which produces
favourable consequence
 favourable consequence strengthen relationships between discriminative
stimulus and response
● distinguished in following way:
 preceding event (discriminative stimulus) sets occasion for responing
because, in past wehn stimulus occured, response was followed by certain
coonsequences
 response we make is called operant behaviour
 following event is consequence for operant behaviour
● consequences are contingent on behaviour
● once operant behaviour is established, it occurs every time discrminative
stimulus occurs, even if other aspects of environment change Reinforcement, Punishment and Extinction:
● operant behaviour can be followed by five different kinds of consequences:
positive reinforcement, negative reinforcement, punishment, response cost,
and extinction
Positive reinforcement:
● positive reinforcement – increase in frequency of response that is regularly
and reliably rewarded by an appetitive stimulus
 positive reinforcer - appetitive stimulus that follows response and icnreases
frequency of response
● negative reinforcement – increase in frequency of response that is regularly
and reliably followed by termination of aversive stimulus
 negative reinforcer - aversive stimulus that is terminated as soon as
response occurs and thus increases frequency of that response
● punishment – decrease in frequency of response that is regularly and reliably
followed by an aversive stimulus
 punisher – aversive stimulus that follows a response and decreases
frequency of that response
 several negative side effects:
■ unrestrained use of physical force may cause serious bodily harm
■ punishment often induces fear, hostility, and other undesirable emotions
in people receiving punishment – may result in retaliation against
punisher
■ through punishment, organisms learn only which responses not to make
– punishment does not teach organism desirable behaviour
● response cost – decrease in frequency of a response that is regularly and
reliably followed by termination of an appetitive stimulis
 form of punishment
 time out of positive reinforcement (omission) – procedure that produces
response cost when it is used to remove a person physically from an activity
that is reinforcing to that person
 punishment causes behaviour to decrease whereas negative reinforcement
causes behaviour to increase
● extinction – decrease in frequency of previously reinforced response because
it is no longer followed by a reinforcer
 different from forgetting – when behaviour is not rehearsed (or memory not
thought about for a long time)
Other Operant Procedures and Phenomena:
Shaping:
● shaping – reinforcement of behaviour that successively approximates desired
response until that response is fully acquired
 to begin, one must be able to recognize target behaviour
 changing criteria in training an animal to perform complex behaviour
Intermittent Reinforcement:
● intermittent reinforcement – occassional reinforcement of particular
behaviour; produces responding that is more resistant to extinction
 follows 2 patterns:
 each response has certain probability of being reinforced ■ probability-based patterns
■ require a variable number of responses for each reinforcer
■ number of responses is related to reinforcer (more responses = more
reinforcement)
■ ratio schedule of reinforcement – apparatus controlling operant chamber
may be programmed to deliver reinforcer after a certain number of
responses
■ if ratio is constant, animal will respond rapidly, receive reinforcer, pause
a little while, and then begin responding again
● called fixed-ratio schedule – schedule of reinforcement in which
reinforcement occurs only after fixed number of responses have been
made since previous reinforcement (or start of session)
■ if ratio is variable, averaging a particular number of responses but
varying from trial to trial, animal will respond at steady, rapid pace
● called variable-ratio schedule – schedule of reinforcement similar
to fixed-ratio schedule but characterized by variable response
requirement having a particular mean
 responses are reinforced after particular intervals of time have elapsed
■ response is reinforced only after particular time interval has elapsed
■ interval schedule of reinforcement – after various intervals of time, a
response will be reinforced
■ if time intervals are fixed, animal will stop responding after each
reinforcement – learns that responses made immediately after each
reinforcement are never reinforced
● called fixed-interval schedule – schedule of reinforcement in whcih
first response that is made after fixed interval of time since previous
reinforcement (or start of session) is reinforced
■ if time intervals are variable, animal will respond at slow, steady rate –
that way it will not waste time and energy on useless responses but
won't miss opportunities for reinforcement either
● called variable-interval schedule – schedule of reinforcement
similar to fixed-interval schedule but characterized by variable time